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277 Cards in this Set
- Front
- Back
Rocks rich in silica
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Silicic
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Rocks rich in iron and magnesium
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Mafic
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Rocks super rich in iron and magnesium
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Ultramafic
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In between silicic and mafic
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Intermediate
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Crust contains what type of rock? continental and oceanic..
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continental - silicic
oceanic - mafic |
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Mantle contains what type of rock?
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Ultramafic
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Outer and Inner core contain what type of elements?
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Outer - Liquid Fe and INi
Inner - Solid Fe and Ni |
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Igneous rocks formed by:
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solidification of a melt
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Magma
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melt in the interior of the Earth - the second it reaches the surface it's not magma anymore
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Lava
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melt at the surface of the Earth
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Between what temperatures will rocks melt under surface conditions
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Between 650 and 1100
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How how is your household oven
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500 degrees Celsius
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The inner core reaches what temperature?
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4300C
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The Lithospheric mantle ranges from what temperatures?
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500-12800
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The crust ranges from what temperatures?
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0-500C
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How do rocks of mantle remain solid?
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they are under extremely high pressure
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Heat-transfer melting
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By increasing the temperature you will reach the point at which rocks melt even under high pressure
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Decompression melting
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By reducing pressure you decrease the melting point of the rocks
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Flux Melting
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Adding volatile elements like water or co2 decreases the melting point of rocks
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Where does heat-transfer melting take place
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Up through the lithospheric mantle where magma melts the surrounding rock
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Where does flux melting occur?
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Water and co2 get squeezed out of subducting slab at subduction zones
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Intrusive Igneous rocks
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solidified inside the Earth from a magma - coarse grained
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Extrusive igneous rocks
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solidified on the surface of the Earth from a lava, fine-grained
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Why do igneous rocks have different compositions?
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because they solidified from melts with different compositions
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Granite composition
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66-76% silica, silicic
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Diorite composition
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52-66% silica, intermediate
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Gabbro composition
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45-52% silica, mafic
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Peridotite (mantle rocks) composition
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38-45% silica, ultramafic
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Three ways of getting magma of different compositions?
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Partial melting, fractional crystallization, Magma contamination
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Partial Melting
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only some minerals add to the composition of the new melt because not all minerals melt at the same time
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Fractional crystallization
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in magma chambers, heavy magma sinks to the bottom - not all minerals crystallize at the same time so only some actually stay in the rising magma and make it to their destination
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Magma composition
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As magma travels up to surface, light felsic crustal rocks break off into the flow of magma and melt, enriching upstream flow with silica
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Dike
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rock feature that cuts across layers
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Sill
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Pushes between layers of rock
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Laccolith
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Blister-like sill that pushes up overlying layers
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Pluton
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Also called batholiths, usually refer to a distinctive mass of igneous rock
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Ability of lava to flow depends on its
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viscosity
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the more viscous a substance is, the faster/slower it flows
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slower
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water has high/low viscosity
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low
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honey has high/low viscosity
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high
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The more silica the lava contains, the greater/lower its viscosity
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greater
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Viscosity of lava depends on its content of
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silica
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What does a highly viscous lava flow look like?
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dome-like shape, travels little distance
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What does an intermediately viscous flow look like?
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thick flow, travels some distance
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What does a fluid lava flow look like?
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thin flows, travels great distances
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What are the two types of eruptions?
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Explosive (gray) eruptions, effusive (red) eruptions
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What level of viscosity results in an explosive (gray) eruption?
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HIGH viscosity
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Why does viscous lava explode more?
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Gas escapes slower from a viscous lava so more gets trapped
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What happens to bubbles of gas as they move up to lower pressure
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They expand and become HUGE
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Part of the volcano where the the main lava pipe comes out
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Summit vent
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part of the volcano where an auxillary flow of magma comes
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flank vent
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underground cavity of magma under the volcano
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magma chamber
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Silica: low
viscosity: low Gas content: low Type of flow: thin |
shield volcanoes
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Shield volcano type of eruption:
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primarily effusive lava flows
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Silica: Intermediate
Viscosity: Intermediate Gas content: Intermediate Type of flow: Thin |
Cinder cone volcano
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Cinder cone volcano type of eruption
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very explosive at vent, effusive lava flows
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Silica: high
Viscosity: high Gas content: high Type of flow: thick, dome |
Stratovolcano
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Stratovolcano type of eruption
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Primarily explosive pyroclastic eruptions
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What do stratovolcanoes look like?
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Very large cone-shaped mountain
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Granite, diorite gabbro - intrusive or extrusive?
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Intrusive
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Name three extrusive rocks
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Rhyolite, Andesite, Basalt
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How many plate interact at the Cascades?
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three
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What type of volcanoes are the Cascades?
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Stratovolcanoes (big mountains)
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What are the layers of a stratovolcano
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alternating eruptions of explosive pyroclastic material and effusive lava flows
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Which type of volcano is prone to landsliding?
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Stratovolcano
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What does volcanic ash consist of
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microscopic particles of rock shards and glass
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What is a lahar
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fast-moving mudflow-likes slurry of ash, debris, and water
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Biggest hazards of stratovolcanoes
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Ash fall, pyroclastic flows, lahars, and landslides
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How far are the Hawaiian Islands from the nearest plate boundary?
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3520 km
|
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What's going on with Hawaii?
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Hot spot - part of a volcanic mountain chain that is largely underwater
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What is a hot spot?
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a location at the base of the lithosphere, at the tope of a mantle plume, where temperatures can cause melting
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What is a hot spot track or train?
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chain of now-dead volcanoes transported off the hot spot by the movement a tectonic lithospheric plate
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What is a hot-spot volcano?
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not caused by movement of a plate boundary - malting of a mantle plume
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What is the Hawaiian Island Seamount Chain?
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Undersea mountain range where Hawaii is - starts in North/South direction then turns more laterally
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How did the Seamounts form?
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Stationary hot spot - Pacific plate was moving north until 43 million years ago - changed to a NW direction 40 million years ago
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Which plate are the Hawaiian islands smack in the middle of?
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The Pacific Plate
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How many volcanic centers are there in Hawaii? active-dormant
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3 active, 14 dormant
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How many Hawaiian islands are there?
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8
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What are the active volcanoes in Hawaii?
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Mauna Loa, Loihi, and Kilauea
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How big are hotspots generally?
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hundreds of kilometers wide
|
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When did Mauna Loa last erupt?
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1984
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When did Loihi last erupt?
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1996
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Which volcano in Hawaii is still producing lava flows?
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Kilauea
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Which of the Hawaiian volcanoes is the youngest and is still underwater?
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Loihi
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What is the crater associated with the Kilauea volcano?
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Pu'u 'O'o Crater
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When did Kilauea last erupt?
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1982
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How high is Loihi as measured from the sea floor?
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3000 meters
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When was Loihi first identified as a volcano?
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1970
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When was the first eruption of Loihi?
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1996
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What are pillow basalts?
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Blob-like shaped pieces of lava formed under water
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What are the major hazards of red volcanoes?
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Lava bombs, lava flows - pahoehoe and Aa
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Explain lava bombs and why they occur
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Although lava has lost most of its gas content by the time it reaches the surface, there is still some that causes explosions - lava bombs are bits of lava that cool before hitting the ground
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What are Pele's tears?
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lava that cools so fast that they turn into black glass
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What trails behind lava bombs?
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Hair thin pieces of cooled lava
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How far can lava bombs fly?
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Hundreds of meters from the vent
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What are the two types of lava flows?
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Pahoehoe and Aa
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What are pahoehoe flows?
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Drag of fluid inside lava flow pulls the surface into ropy ridges
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What are Aa flows?
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rubbly flow with jumbled angular pieces - too thick to turn to ropes - distal edge of lava flow
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Where did the name Aa come from (myth)?
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people walking over them and saying "ah ah ah"
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Explain catastrophism
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Basically the idea that the processes that laid down rocks were biblical floods in some capacity
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"processes that laid down rocks are no longer with us"
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Catastrophism
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What did most naturalists think about Noah's flood by the late 1700s?
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Most naturalists didn't take the story literally
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Who was the famous friend of James Hutton?
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Adam Smith
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What theory did James Hutton propose?
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Uniformitarianism
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Define uniformitarianism
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The slow, gradual processes that are shaping the geology of our planet today are sufficient to explain the geology of the past
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When did James Hutton live?
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1726-1797
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Who was the strict-uniformitarianism that did not believe in any catastrophes?
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Charles Lyell (1797-1875)
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"cumulative slow change produced by natural processes operating at RELATIVELY CONSTANT RATES" - who would have said this?
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Charles Lyell
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True/false - Hutton argued that slow, gradual processes are the only things shaping geology
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false - he thought it was a combination
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What did Hutton think were a result of catastrophe?
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mountains
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What first led Hutton to the idea of gradual change?
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beach erosion
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Neocatastrophism?
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sudden, high magnitude events do happen - but gradual processes are as important - laws of the universe do not change
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How is clastic sedimentary rock formed?
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mineral material that precipitated between the grains and "glued"/cemented them together
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How is crystalline sedimentary rock formed?
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chemicals are transported in solution, then when water evaporates the grains tightly interlock with one another like a jigsaw puzzle
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What does cemented texture look like?
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layers
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What are clastic sedimentary rocks?
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Cemented together fragments of pre-existing rocks
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What are chemical sedimentary rocks and what kind of texture do they have?
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Precipitation of crystals out of a solution - interlocking
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What are the two types of sedimentary rock textures?
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Cemented, interlocking
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What are biogenic sedimentary rocks?
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clasts/grains consisting of skeletal material - underwater from bones of shellfish
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Why are grains from a desert environment frosted?
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Because the wind blows them around so they scratch each other a lot
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Where is the world's biggest desert?
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Antarctica
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Sand grains transported by water are ?
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highly polished
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Discuss well-sorted vs. poorly sorted grains
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wind has a narrow size range that can be carried, unlike water. Most sediments in the desert, carried by wind, are "well-sorted" because there is a narrow range of size that wind can transport
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What is the stoss side
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The side facing the wind - the side the wind blows up
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What is the lee side?
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The side on which grains are dumped - faces the direction in the dune will move
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What are cross-beds?
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Areas where you see tons of crossing sedimentary layers because each dune has layers in itself and then you could have hundreds of moving layers in each desert
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Where is there a big cross-bed and why is it there?
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Zion National Park, UT - deposited when North America was at the the heart of Pagaea in a huge desert rainshadow
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How tall were some of the dunes in the desert in N. America when Pangaea existed?
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kilometers high
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Why do you find very few terrestrial fossils in desert environments?
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Things get eaten very quickly, little life to begin with
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What do you find in desert rocks instead of fossils?
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Tracks
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How do tracks get fossilized?
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Dew in the morning causes tracks to glue together and get baked in the sun - quickly covered with sand from elsewhere and preserved that way
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What are evaporites?
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sedimentary rocks or minerals that form by evaporation of a solution enriched in minerals
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What do evaporites look like in the rock record?
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spaces left behind by evaporite minerals that dissolved after the sediment had hardened
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How do evaporites form?
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puddles form and create a solution - water evaporates and gypsum crystals form - get buried and can become lithified
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What do evaporites tell you?
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There must have been a very hot environment
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What do you see in a core sample from a lake?
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Alternating layers of light and dark laminations formed by the very fine-grained sediments that make it to the center of the lake
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Why are there alternating colors in a lake core sample?
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During summer, lake gets a lot of fine/light sediment - during fall/winter, lake gets a huge carbon influx as stuff dies
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In a lake core sample, what do the light and dark layers signify
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light - summer, dark - winter
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Why are lake environments geologically ephemeral?
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they eventually fill up with sediment
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What is a varve?
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A lamination
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How can you determine the age of a lake
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count the number of laminations/varves like tree rings
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What are metamorphic rocks?
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What rocks permanently turn into when they are altered by heat and pressure
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What is physical deformation?
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Normal physical stress - compression and extension
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What is change in physical deformation of rocks?
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the physical shape of the grains
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Explain shear stress
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Rock is pushed in 2 opposite directions and everything is skewed - on an atomic scale you create shear planes
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What are chemical changes of rocks?
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Run superhot fluids through the grains of a rock - grains fuse and recrystallize, usually into bigger grain-size crystals
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what is a solid-state phase change
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Same exact elements but different arrangement - results in different properties
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How does the crystal structure of atoms in minerals change during a solid-state phase change?
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Instantaneously
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Polymorphs
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Crystals of the same mineral but with different atomic structures
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With increasing pressure, alpha-quartz turns to...
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beta-quartz, then into coesite
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What is neocrystallization?
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At the right pressures/temperatures, completely new minerals can form - chemical reactions (weathering) digest the minerals of the original rock which yields new minerals
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What is an example of neocrystallization?
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Garnet - combination of quartz, iron oxide, and micas
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Pressure solution metamorphism
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At low temp/pressure minerals dissolve at pressure surfaces between grains, causing grains to fuse together
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What are the four processes of metamorphic change?
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Recrystallization, phase change, neocrystallization, pressure solution
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Foliated metamorphic rocks
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Flattened grains, expanded horizaontally - all grains turned into pancakes - is a type of grain organization
|
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What type of rock is slate?
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Foliated metamorphic
|
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As you increase pressure, what does mudstone turn into?
|
Mudstone -> slate -> phyllite -> schisst -> Gneiss
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How do you know if a metamorphic rock is foliated?
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They exhibit some form of mineral alignment due to shear or normal stress
|
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Formation of Marble
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Recrystallization of limestone occurs and the grains/fossils are destroyed - marble retains original composition - no mineral foliation
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Formation of quartzite
|
Quartz-rich sandstone (SiO2) - recystallization + pressure solution = grains fuse into interlocking texture
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What does quartzite look like?
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giant lumps of quartz with a mottled surface texture when broken
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Why doesn't quartzite take on foliation?
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resistance of quartz grains to deformation, and lack of elements available inside the protolith for neocrystallization to form micas
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Hornfels
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non-foliated metamorphic rocks that are the result of heating and little to no pressure
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How do hornfels usually form?
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As the result of "baking" by an igneous intrusion into shallow crustal rocks (less than 3 km deep)
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What are the common nonfoliated metamorphic rocks?
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Marble, quartzite, hornfels
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Where do neocrystalline grains grow in foliated metamorphic rocks?
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Perpendicular to stress
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What are reasons for metamorphic rocks not taking on foliation?
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Minerals that resist deformation or recrystallize w/o preferred orientation, rocks experiencing too little stress, protoliths lacking minerals that could provide elements for neocrystallization of aligned minerals
|
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Formation of Marble
|
Recrystallization of limestone occurs and the grains/fossils are destroyed - marble retains original composition - no mineral foliation
|
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Formation of quartzite
|
Quartz-rich sandstone (SiO2) - recystallization + pressure solution = grains fuse into interlocking texture
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Difference between faults and folds?
|
Faults - brittle deformation
Folds - ductile deformation |
|
What does quartzite look like?
|
giant lumps of quartz with a mottled surface texture when broken
|
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Why doesn't quartzite take on foliation?
|
resistance of quartz grains to deformation, and lack of elements available inside the protolith for neocrystallization to form micas
|
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Hornfels
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non-foliated metamorphic rocks that are the result of heating and little to no pressure
|
|
How do hornfels usually form?
|
As the result of "baking" by an igneous intrusion into shallow crustal rocks (less than 3 km deep)
|
|
What are the common nonfoliated metamorphic rocks?
|
Marble, quartzite, hornfels
|
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Where do neocrystalline grains grow in foliated metamorphic rocks?
|
Perpendicular to stress
|
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What are reasons for metamorphic rocks not taking on foliation?
|
Minerals that resist deformation or recrystallize w/o preferred orientation, rocks experiencing too little stress, protoliths lacking minerals that could provide elements for neocrystallization of aligned minerals
|
|
Difference between faults and folds?
|
Faults - brittle deformation
Folds - ductile deformation |
|
What types of folds form from compressional stress?
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Synclines, Anticlines, and Monoclines
|
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Which type of fold is like a Smiley face?
|
Syncline
|
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Which type of fold is like a mountain
|
Anticline
|
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Which type of fold is just like a wavy line
|
Monocline
|
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What is an angular fold with straight things
|
Chevron folds (syncline or anticline)
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What type of structure is the lady's cave?
|
Chevron fold
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What is the part of a fault that is uncovered by the land slipping away? (diagonal)
|
Fault plane
|
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What do you call the distance the land fell in a fault?
|
Fault scarp
|
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What is the edge lining the fault plane called?
|
Fault trace
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Which "wall" is the one that stays still?
|
Footwall
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Which "wall" is the one that is fattest on top?
|
Hanging wall
|
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In a normal fault, in which directions do the "walls" move?
|
Hanging wall moves down, footwall moves up
|
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In a reverse fault, in which directions do the "walls" move?
|
Hanging wall moves up, footwall moves down
|
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In a transform fault, in which directions do the "walls" move
|
Sideways (footwall towards you, hanging wall away?)
|
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What faults are associated with the term dip-slip?
|
Reverse fault, normal fault
|
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What fault is associated with the term strike-slip?
|
Transform fault
|
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Type of stress associated with reverse fault
|
Compressional
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Type of stress associated with normal fault
|
Extensional stress
|
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Type of stress associated with transform fault
|
Shear stress
|
|
Thrust fault
|
Gently dipping reverse fault - layer of older rock laid on top of older rock
|
|
Intraplate fault
|
Small fracture in interior of plate - pressure can build up and cause earthquakes
|
|
What proportion of earthquakes occur along plate boundaries
|
about 99%
|
|
Earthquakes along mid-ocean ridges
|
there are large fracture zones along the mid-ocean ridge - you can get slippage/movement on transform faults that cas
|
|
How do earthquakes happen?
|
Faulting causes pressure buildup and when it fails, you get seismic waves
|
|
Analogy for surface waves
|
Surface of water when you drop a pebble in
|
|
Analogy for body waves
|
Energy that propagates through the interior of the water when you drop a pebble in- can't see
|
|
Besides tectonic earthquakes, what kinds are there?
|
Volcanic, collapse (landslide or cave collapse), impact explosion (nuclear detonations, fuel plant explosions),
|
|
What are the most common types of natural quakes?
|
Tectonic and volcanic
|
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What is the point of the earthquake where the disturbance occurs (underground)?
|
Focus
|
|
What is the point on the surface directly above the focus?
|
Epicenter
|
|
How do shear waves move?
|
Particles move up/down or left/right
|
|
How do compressional waves move?
|
particles move back and forth parallel to the direction of wave motion
|
|
What are the four types of waves?
|
Compressional body waves (p-waves), shear body waves (S-waves), Shear surface wave type I (r-wave), Shear surface wave type II (L-wave)
|
|
What is the primary, fastest-moving type of seismic wave?
|
P-waves (compressional body)
|
|
What is the secondary wave?
|
S-wave (shear body)
|
|
describe a Rayleigh wave
|
circular surface wave - magnitude decreases with depth
|
|
Describe a Love wave
|
Side to side surface wave - decreases with depth
|
|
What are the major hazards during an earthquake?
|
Ground shaking, landslides, and liquefaction
|
|
What are the major hazards after an earthquake?
|
Fire, disease
|
|
What is pancaking of buildings?
|
floors of a building collapse on each other because the columns in between aren't strong enough to withstand shaking
|
|
Ground shaking is primarily caused by which type of waves?
|
Shear waves
|
|
What type of ground surface expresses seismic waves the strongest?
|
Water-logged sediment
|
|
Where is one of the safest places to be during an earthquake?
|
a mine
|
|
What type of column is made now that can withstand earthquake shaking
|
Concrete inside a steel jacket - even if the concrete crumbles it is still contained
|
|
What U.S. areas are in major danger of landslides from earthquakes?
|
Southern CA to L.A. with expensive real estate, place where the Great Alaska Christmas earthquake happened
|
|
What is liquefaction
|
water-logged soils turn to slurry when shaken by earthquakes
|
|
What are sand blows
|
Cracks or holes in the ground open up when liquefaction occurs, and water gushes out above where a slurry has been created/shaken up
|
|
What is the big problem with fires after earthquakes/
|
Since there is so much debris everywhere, it's very hard to get to fires to put them out - lots of times hydrant pipes have been broken also
|
|
Two examples of huge fires after earthquakes
|
1906 San Francisco - Kobe, Japan
|
|
What has Kobe, Japan done to counter dangers of fires with earthquakes
|
Have built underground steel tubs filled with water every two blocks
|
|
Examples of really bad disease outbreaks after earthquakes
|
Haiti, Pakistan, Indonesia
|
|
What is the recorDER of earthquakes
|
seismometer
|
|
What is the recordING of earthquakes?
|
Seismogram
|
|
What is the I-XII intensity scale and who invented it?
|
Giuseppe Mercalli - 12 categories to describe the damage done by an earthquake
|
|
What does the Mercalli Intensity Scale range from
|
I-XII
|
|
problems with Mercalli scale
|
buildings respond differently, varies depending on distance from epicenter, relies on eyewitness reports
|
|
Why is there minimal shaking in Appalachian mountains during an earthquake?
|
It is underlain by hard metamorphic rock
|
|
how does the Richter scale work?
|
Measures the relative amount of energy released by determining the amplitude of the largest ground motion
|
|
Biggest problem with Richter scale
|
Loses resolution for quakes >7.0 (also only uses one source for data)
|
|
What is the earthquake scale we use today?
|
Moment Magnitude Scale
|
|
An increase of one unit of magnitude on the Richter scale equals:
|
33 times more energy
|
|
What things does the Moment Magnitude Scale include in its calculation?
|
Length of the fault rupture, area of rupture surface, and shear strengths of rocks
|
|
Igneous rock formation
|
formed as solidifications of a melt
|
|
Do silicic and felsic rocks have any Mg or Fe in them?
|
yes, but proportionately more silica
|
|
How does rock composition relate to the temperature required to melt it?
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Generally, more Fe and Mg require higher temperature to melt
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Why don't rocks in the mantle melt?
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Because they are at such high pressures
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Decompression melting
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Parcel from mantle moves fast enough up to the lithospheric mantle, pressure change causes melting
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heat transfer melting
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melt flows into cracks and burns its way through the lithosphereic mantle
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What percentage of parcels from the mantle never make it to the surface?
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90% - because they usually go cold before reaching crust
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Intrusive igneous rocks
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solidfy inside the Earth - have time to arrange themselves into intricate crystal patterns
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Relationship between grain size and cooling time?
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Rapid cooling - fine grained, slow cooling - coarse grained
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Generally, of what grain size are volcanic rocks?
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Fine-grained
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How fast do convection cells of magma move?
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one rotation takes hundreds of thousands of years
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Partial melting
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not everything melts at the same temperature - silica minerals melt more easily
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How does magma chamber differentiation happen?
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Mafic minerals crystallize before silicic minerals - so magma becomes more silicic and the crystallizes mafic minerals sink to the bottom of the less dense magma chamber
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Magma Assimilation/Contamination
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Silica crust breaks off and melts into the magma flow, adding lots of silica to the magma
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Dike intrusion
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sheet of igneous rock that cuts discordantly across rock structures/formations
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Sill
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too much magma in a dike expands laterally between layers
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Laccolith
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sill fills more and warps the layers up above
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Pluton
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irregular blob of magma that never reaches surface
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Category of "plutons" includes:
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batholiths, dikes, sills, laccoliths, other igneous bodies
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Most fluid type of lava has what kind of composition?
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Most magnesium and iron
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What type of lava tends to lead to really explosive eruptions?
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Viscous - high in silica
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What is an effusive eruption like and where do they occur?
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fluid - typical of Hawaii - hot spots
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Why does viscous lava make bigger explosions?
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Giant bubbles of gas form and can't escape - then they dramatically expand as pressure decreases
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Flank vents - what are they, when do they happen?
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kind of like an escape route for lava - happen when main vent is plugged up with old magma
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Where are there shield volcanoes in the U.S.?
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Hawaii
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Where are there stratovolcanoes in the U.S.?
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the Cascades (WA, OR)
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Where are there cinder cone volcanoes in the U.S.?
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In the Southwest but they are largely inactive
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What is the number one hazard associated with stratovolcanoes?
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Big chunks break off since stratified layers cause the mountain to be unstable
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What is the last volcano to have erupted before St. Helens?
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Lassen
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What type of plate boundary are the Cascades near?
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Subduction zone
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When did Mt. St. Helens erupt?
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1980
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What was the level of the earthquake produced by the St. Helens eruption/
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3.0
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How far did the landslide after Mt. St. Helens travel?
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50 miles
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How fast do pyroclastic flows travel?
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150-180 mph
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Worst pyroclastic flow
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1902 - St. Pierre on Island Martinique - killed everyone but 2
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Lahar flows
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result of stratovolcano erupting during higher rainfall - steaming, boiling mud flow 100s of degrees hot
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Most famous Lahar flow
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Colombia in the 80's that covered the whole village
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